The present invention relates to soldering apparatus and more particularly, to an apparatus which will automatically supply a fresh quantity of soldering material to an article to be soldered.
It is known to use soldering baths where the soldering operation is carried out automatically, for example, on the ends of coil wires on the bodies of electromagnetic coils which are provided with connecting pegs for the lead line. In such apparatus, the problem of oxide formation on the surface of the soldering bath has complicated the automatic sequence of the operation. In addition, changes in the solder bath where a tin alloy is being used have occurred which result in electrical connections which are inferior. The degradation of the tin alloy bath is due to the repeated submergence of the elements being soldered into the soldering bath. In attempting to solve these problems, the prior art has suggested the use of scrapers moving over the surface of the solder bath to remove the oxide layers, on the one hand, and on the other hand, the use of a lid which covers the bath except during a soldering operation. In such arrangements, the amount of soldering material that is lost increases in direct proportion to the frequency of the scraping of the surface of the bath.
The foregoing disadvantages are avoided by the present invention which provides a soldering apparatus which repeatedly presents a properly alloyed bath to the elements to be soldered by use of a separate ladle having a solder bath tank which is submerged in a vessel containing a large quantity of solder bath material and where, by the act of submergence, the soldering material in the separate tank is replenished.
In a preferred embodiment, the advantages of the present invention are obtained by the use of a ladle having a soldering bath tank which is communicated adjacent its bottom with a separate scoop whereby the upper lip of the scoop lies in a horizontal plane that is vertically spaced above the upper lip of the tank. The tank and the scoop are movable jointly by a mechanism that raises and lowers the ladle periodically relative to the vessel containing the molten solder bath.
Since the scoop and the solder bath tank are in flow communication by means of a pipe, which extends from the bottom of the scoop to the bottom of the tank, the bath level in the scoop will drop as the scoop and tank are lifted out of the solder bath vessel. Since the tank will already be completely filled by virtue of its submergence into the bath of the vessel, the solder bath material will overflow the upper lip of the soldering tank by a predetermined quantity until the level of solder bath in the scoop equals the level in the tank. As a result of the surface tension of the molten soldering material and the dimension of the tank, a meniscus or bubble will develop over the surface surrounded by the upper lip of the tank. By a proper selection of the dimensions of the tank, and proper regulation of the heat of the solder bath, the configuration of the meniscus will be repeatable within close tolerances upon each submerging and raising of the tank and scoop from the solder bath. This will greatly simplify the soldering operation where, for example, elements are automatically positioned above the solder bath and submerged into the meniscus of soldering material when the tank is raised from the solder vessel. The quality of the soldering will be improved by the fact that the soldering material in the tank will contain only fresh solder material by virtue of the submergence of the scoop and solder tank into the main vessel bath and the overflow of solder caused by the difference in height of the scoop above the upper lip of the tank when the scoop and tank are raised from the main solder bath.
By the proper dimensioning of the scoop and the soldering bath vessel, the exposure time for the tin outside of the main bath can be maintained at a much shorter interval than has previously been the case. Also, by close dimensioning of the diameter of the solder bath tank as well as its horizontal distance from the scoop, the apparatus of the present invention can be employed to effect soldering where space limitations are significant such as is the case with connecting pegs or lead lines which are of a very short length on the bodies of electromagnetic coils.